1. Field of the Invention
The present invention relates to a technique for taking countermeasures against factors such as a variation in a vehicle body and attachment errors of vehicle height detecting means, thereby guaranteeing reliable irradiation control in an irradiating direction control device for a vehicle lamp which is constituted to detect a vehicle height displacement for the axle portion(s) of a front wheel and/or a rear wheel in a vehicle to obtain a change in a vehicle attitude, and to control the irradiating direction for the vehicle lamp depending on the change.
2. Description of the Related Art
There has been known a device (a so-called autoleveling device) for always correcting the irradiating direction of a lamp to cancel the influence of a change in a vehicle attitude in order to prevent the direction of the irradiated light of the lamp provided in the vehicle from being unstabilized by the change in the attitude in the direction of advance of the vehicle dulling stop or running of the vehicle.
For example, there has been proposed a device for calculating a vehicle attitude (a pitch angle) based on a detection signal measured by vehicle height detecting means provided for the axle portion of a front wheel or a rear wheel and driving the reflecting mirror of a lamp in such a direction as to offset the change, thereby automatically adjusting an optical axis.
In a general vehicle height measuring method, a vehicle height sensor for measuring a distance between an axle and a vehicle body is used. An actual vehicle has various errors (for example, the assembly error of a vehicle, the attachment error of a vehicle height sensor, and the error of the vehicle height sensor itself such as an error made by a variation in a sensor output origin). Therefore, the result of an operation of the vehicle attitude is influenced so that a pitch angle thus calculated includes an error, for example. Since the error can be absorbed by the initial adjustment of a lamp (aiming adjustment), it is not reflected as a shift from the optical axis of the lamp.
However, a method of taking countermeasures against the error factors by only the aiming adjustment is limited and has the following problems, for example.
Referring to an actuator for driving a reflecting mirror in a lamp, it is necessary to maintain a movable range taking an error into consideration. For example, the moving stroke of the actuator is great in a lamp having a long lamp span to be a distance between a rotating fulcrum (or a tilt fulcrum) in a movable reflecting mirror and an actuator fixing portion (connecting portion). Therefore, there is a drawback that a moving margin for absorbing an error cannot be sufficiently maintained or a sufficient stroke cannot be obtained due to the maintenance of the moving margin. The same drawback is caused in a vehicle having a short wheel base. More specifically, in such a vehicle, a change in a pitch angle is great. For this reason, the moving stroke of the actuator is to be increased.
The stroke of the actuator is set to be xe2x80x9ca stroke required actually for the driving control of a reflecting mirror (a stroke for a design)+error X2xe2x80x9d (the xe2x80x9cX2xe2x80x9d portion depends on the necessity for considering a stroke corresponding to the same error in the directions of protrusion and retreat of the actuator). In the case in which the stroke is set to be constant, therefore, a strain is put on a necessary stroke if a stroke for absorbing an error is excessively increased. As a matter of course, there is no problem if a total stroke including xe2x80x9cerror X2xe2x80x9d can be always maintained. In the case in which the arrangement space of the lamp or the actuator in the vehicle is restricted, such a guarantee cannot be always obtained.
In the case in which a loading space is not mounted at time of shipping from a factory but is mounted by a mounting dealer according to uses after the shipping as in a motor truck, the attitude of a vehicle of the same type is greatly varied depending on a mounting condition. However, it is impossible to predict a change in the vehicle attitude which is caused by the mounting. Therefore, the moving margin for difference absorption cannot be set in advance. Accordingly, the countermeasures cannot be taken by the conventional method.
In the case in which the influence of various error factors cannot be eliminated sufficiently, accordingly, there is a possibility that the change in the vehicle attitude might be neither detected nor recognized accurately, resulting in a deterioration in control precision in an irradiating direction.
Therefore, it is an object of the invention to eliminate a variation in precision in attachment of vehicle height detecting means to a vehicle body and the influence on the detection of a vehicle attitude which is caused by an individual difference in the vehicle.
In order to solve the problems described above, the invention provides an irradiating direction control device for a vehicle lamp which carries out an operation for a vehicle attitude based on detection information obtained by vehicle height detecting means and changes an irradiating direction of the lamp depending on the vehicle attitude, comprising nonvolatile storage means for storing data indicative of an actual vehicle height value in a reference state of the vehicle attitude or a difference between the vehicle height value and a vehicle height value for a vehicle design, and irradiation control means for obtaining the vehicle attitude by an operation from vehicle height data corrected by using the data stored in the storage means for the detection information obtained by the vehicle height detecting means and controlling the irradiating direction of the lamp to cancel an influence of a change in the vehicle attitude based on a result of the operation.
According to the invention, therefore, the data indicative of the actual vehicle height value in the reference state of the vehicle attitude or the difference between the actual vehicle height value and the vehicle height value for a vehicle design are stored in advance, and the tilt of the vehicle attitude can be obtained based on the vehicle height data corrected by the stored data during irradiation control and the irradiating direction of the lamp can be controlled correspondingly.